The signals transmitted in wireless communications systems often vary in strength and thus require the use of variable gain amplifiers in the radio transceiver. These variable gain amplifiers operate to compensate for changing path losses in the transmitted signal.
Ideally, the variable gain amplifier (VGA) provides amplification at low noise levels, adds little distortion, and consumes very little power. This is important because any distortion produced by the transmitter spills power into adjacent communication channels and thereby reduces system capacity. To minimize distortion, the bias current in the VGA and other circuits is typically high—an unwanted attribute for portable devices.
It would therefore be advantageous to have a VGA with low distortion and low power consumption.